On average, the more religious you are, the more kids you’ll have. It’s a widespread phenomenon, seen across pretty much all of the modern world.

The problem is, no-one really knows why this happens.

It could be something about religious beliefs. Maybe they make you more attractive to potential mates, or maybe they drive you to have more kids once you have found your mate.

Or maybe they encourage traditional, rather than modern, approaches to relationships. The traditional role for women is to stay at home and raise children, while hubbie has a career (and the independence and money that goes with it). It works (in theory at least) because divorce is not allowed, meaning that women cannot be left financially adrift.

Berghammer found that people following the ‘traditional’ lifestyle were more to have 3+ children than those following the ‘modern’ lifestyle. What’s more, traditionalist individuals were more likely to be religious (all Catholic in this analysis).

But – and this is the crucial bit – among those who followed a traditional life path, there was no relationship between their depth of religious belief, or their Church attendance, and the number of children they had.

Exactly the same was seen for those following a modern life path. Although this was more popular among non-religious women, those religious women who did follow this trajectory had no more children than the non-religious.

There was also no difference between the religious and non religious in the chances of remaining single and childless.

Berghammer concludes from this that the critical factor in determining fertility is the choice of life trajectory. Once this has been decided, then religiosity has no further effect on fertility.

The model here is then that religiosity shifts the probability of one following a particular life path, but that there is no marginal return on religiosity once that life path is chosen. This sounds broadly plausible to me. It explains how more religious societies such as Greece, Italy, or Spain, could have lower fertility rates than more secular societies such as Iceland or Finland. There are lots of variables which go into determining life path, and the average between society differences can have a big impact on the distribution of fertility. Though within societies the religious on average seem to be more fertile. Or do they? Again we need to be careful as different societies have different correlations.

Here’s some data from the World Values Survey Wave 5. I limited the sample to those age 50 or over.

The Netherlands has the largest disjunction between fertility in those who view religion as important, and those who do not. I suspect this is due to the advanced secularization in the Netherlands, and, the existence of a cultural Bible Belt where higher fertility is normative. What’s going on in South Korea? To understand this you need to know that Europe and South Korea in some ways have gone through inverse cultural processes since World War II. Europe has de-confessionalized as belief in, and support for, institutional religion has collapsed in many regions. In contrast, South Korea has confessionalized, driven by a Western oriented conservative Protestant movement which went from less than 5% of the population to around 25% in two generations. As in many Confucian dominated societies organized religion generally had been viewed suspiciously by the authorities, and institutional Buddhism specifically had been marginalized in Korean public life for centuries (since the rise of the Joseon)). The emergence of Christian (and also Buddhist to a lesser extent) religiosity in South Korea over the past two generations has been particularly notable among the urban middle classes. In South Korea religious affiliation is higher in urban areas, and Seoul is the most Christianity city in the peninsula (while Busan is the capital of Korean Buddhism). So the most “modern” segment of society is the most the religiously devout, and you see the lower fertility among those who are the least secular.

The more religious, the less intelligent, educated and emancipatd (women).

And the more intelligent, educated and emancipated (women), the fewer children.

Sandgroper

Plus Koreans are weird, violent and very screwed up people. During WWII, the Korean POW guards were notably even more brutal than the Japanese.

You need to see footage of male South Korean “rice farmers” assaulting Hong Kong police women (that’s random MALE people brutally assaulting FEMALE law enforcement officers just trying to keep the peace) (and I’m here to tell you that HK police women are not only very cute and nice people who smell good, they are good, serious, sensible and efficient at their jobs) extremelyviolently with steel bars in massed attacks during a WTO meeting in HK. Never have the HK population been so unanimously in support of their police force.

Nuke ‘em. All of them, North + South. They are a waste of oxygen.

http://www.mazepath.com/uncleal/ Uncle Al

Who is hotter than a polygamommie?

Sandgroper

Who is hotter? Female Communist Chinese Immigration and Cusztoms Officers.

http://www.kinshipstudies.org German Dziebel

As a point of comparison, Russell Thornton argued that the revitalization religious movements among North American Indian tribes in the late 19th century had a positive impact on their demographic recovery by enhancing solidarity and spurring fertility. The Ghost Dance religion literally intended to bring dead Indians back to life through prayers and rituals, and this indeed came true not through miracles but through rising fertility rates. (Notably, reincarnation believes are not very typical among North American Indian tribes.) Ghost Dance was short lived partially because its prophet Wovoka couldn’t obviously literally deliver on the promise, but it did push Native American individuals and families into a specific direction (or life-path) that was demographically successful.

See Thornton, We Shall Live Again: The 1870 and 1890 Ghost Dance Movements as Demographic Revitalization.

So, “religiosity shifts the probability of one following a particular life path, but that there is no marginal return on religiosity once that life path is chosen” seems right to me as well. The question arises: why are there religions that persist after their demographic impact has petered out? We may want to look at the other end of religion’s demographic function, namely it’s ability to “contain violence” (using Rene Girard’s paradoxical terminology to describe the situation when religion can unleash violence or it can restrain violence. In both cases, we’ll have demographic implications.

So, in a word the impact of religion on fertility should be tracked alongside it’s impact on mortality.

The modern world may in fertility terms be as uncharitable to the extremely religious as it is to extreme atheism.

The Amish, who happen to have Dutch ancestry, have made a success of a very religious life in reproductive terms. I wonder if family size tracks religiosity in the Amish community. (i.e. compare liberal Amish to the more traditional Amish community)

Edit: and another thing – perhaps the very religious, whilst not having higher fertility, are having families at a younger age? that would result in higher “turnover” and faster population growth without higher fertility due to shorter time between the generations.

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About Razib Khan

I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. In relation to nationality I'm a American Northwesterner, in politics I'm a reactionary, and as for religion I have none (I'm an atheist). If you want to know more, see the links at http://www.razib.com